The plastic bag with transparent window is one very common packaging form for food products. The plastic bag is divided into two parts, i.e. print area and non-print area. The non-print area is transparent plastic film, which is like a window and displays the content inside the package to the customers.

Generally, the material of the non-print area is the same as that of the print area. Sometimes, the materials of those two areas are different. Owing to the difference of printings or materials, the barrier property of those two areas are distinct from each other, more or less. Therefore, it is necessary to test the print area and non-print area respectively when examining the barrier property of the plastic bag with transparent window.

This article provides a simplified test method of oxygen barrier property of plastic bag with transparent window for your reference. The testing instrument used for the tests is Labthink’s VAC-V2 Gas Permeability Tester, which adopts differential pressure method where the sample is mounted in a gas transmission cell so as to form a sealed semi-barrier between two chambers. One chamber contains the test gas at a specific high pressure, and the other chamber, at a lower pressure, receives the permeating gas. The gas permeability of the sample can be calculated on the basis of pressure change.

Figure 1. Plastic Bag with Transparent Window

The test specimens are plastic bag with transparent window for peanuts. The tests shall be performed in an environment where the temperature is 23℃ and the humidity is 0%RH, according to the following procedures.

(1)    Cut 3 pieces of specimens from the transparent window area of the provided sample material. The diameter of the specimen shall be 97mm.

(2)    Apply a thin layer of vacuum grease on the outer surface of the test chamber and then place a filter paper on the central area. The diameter of the filter paper should be 65mm.

(3)    Place the 3 pieces of specimens on the test chambers respectively.

(4)    Set test temperature, humidity, specimen thickness and other test parameters. Turn on the vacuum pump and temperature control device. Click Test to start the test.

(5)    The instrument will monitor the pressure change in the lower pressure chamber and calculate the test results automatically.

Figure 2. Mount Specimen

(6) Cut specimens from the printing area and perform tests according to step 2 to 5.

For more details about VAC-V2 Gas Permeability Tester, please visit www.labthink.com

About Labthink Instruments Co., Ltd:

Labthink Instruments Co., Ltd is one leading supplier of packaging testing instruments, which is headquartered in Jinan, China and operated in Boston, U.S.A.